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  • Author or Editor: Ronald F. Slocombe x
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Summary

The lungs of sensitized horses were exposed to aerosolized ovalbumin. Some horses (n = 4) were given ovalbumin in 1 lung only, whereas in others (n = 7), ovalbumin or vehicle were inoculated in the cranial, ventral, and caudal regions of the caudal lung lobe. Horses were exercised 5 hours after ovalbumin exposure. Immediately before exercise, endoscopy failed to reveal any abnormality. After exercise, endoscopic examination of horses subjected to unilateral ovalbumin exposure revealed extensive blood in airways leading to the exposed lung in all horses. Blood was not observed in the airways leading to the control lung. Mean (± sem) minimum volume of the exposed and control lungs was 9.5 ± 1.5 and 5.5 ± 1.6 L, respectively; this difference was statistically significant (P< 0.05). Bronchoscopy of horses subjected to regional ovalbumin or vehicle exposure and exercise revealed a small amount of blood-tinged fluid in the bronchi serving the regions of the lung inoculated with ovalbumin. Minimum volumes of such regions were not significantly different from one another. However, their minimum volume was significantly (P<0.05) larger than that of vehicle-inoculated regions. Gross and histologic examination confirmed inflammation and hemorrhage in the ovalbumin-exposed, but not the control lungs or lung regions. Thus, exercise can cause blood from an injured region of lung to appear in the larger airways. Regional differences in lung structure and function do not influence the appearance of blood in the airways.

Free access
in American Journal of Veterinary Research

SUMMARY

Morphologic changes in equine jejunal segments subjected to 1 hour of ischemia and 1 hour of reperfusion, and protective effects of systemic administration of dimethyl sulfoxide (dmso; 1 g/kg of body weight) were investigated in 18 ponies, using light microscopy and scanning and transmission electron microscopy. Ponies were allotted to 4 groups: group 1—control (n = 3); group 2—dmso (n = 3); group 3—ischemia (n = 6); and group 4—ischemia and dmso (n = 6). In each pony, 2 jejunal sections were evaluated. The first section was obtained prior to induction of ischemia, and the second was obtained 2 hours later after reperfusion. Mucosal lesions were graded from 0 (normal) to 5 (most severe).

Combined ischemia and reperfusion of 2 hours’ duration induced moderately severe mucosal injury to the equine jejunum (group 3; grade 1.5 to 2.5), characterized principally by disruption of enterocyte attachment from the basement membrane and lamina propria. Fluid accumulation disrupted enterocyte cell-to-cell adhesion toward cell bases, while apical tight junctions and desmosomal junctions toward the luminal surface remained intact. Intracytoplasmic organellar changes within enterocytes were not a prominent feature of the injury. The aforementioned processes were marked at the villus tip and progressed down the villus sides. These findings support the importance of mechanisms leading to early sub-epithelial fluid accumulation rather than that of direct severe enterocyte injury. Further, fluid accumulation does not appear to arise from intercellular migration from the luminal surface. In this model, a pathomechanical effect caused by vigorous villus retraction appears to exacerbate epithelial lifting toward the villus tip. Systemic administration of dmso (1 g/kg) prior to reperfusion failed to improve the appearance of the mucosa (group 4; grade 1.5 to 4.0), suggesting that it was ineffective in preventing this form of ischemia-reperfusion injury.

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To determine whether IV administration of furosemide (250 mg) to horses before maximal exercise affected maximal oxygen consumption (V⃙o2max), breathing mechanics, or gas exchange during exercise.

Animals

7 healthy, well-conditioned Thoroughbred horses.

Procedures

5 horses initially performed an incremental treadmill exercise test to determine V⃙o2max 4 hours after IV administration of furosemide (250 mg IV) or placebo (saline [0.9% NaCl] solution). Time to fatigue and distance run were recorded. All 7 horses were then used to determine the effects of furosemide on gas exchange and breathing mechanics at 40, 60, 80, and 100% of V⃙o2max. Horses were weighed immediately before exercise.

Results

Furosemide treatment significantly increased mass-specific V⃙o2max (5.3%), but absolute V⃙o2max was not significantly altered. In the 2 parts of the study, body weights were 2.9 and 2.5% higher when horses were given placebo than when they were given furosemide. Time and distance run at speeds ≥ 11.0 m/s were significantly greater following furosemide administration. Furosemide treatment had no effect on breathing mechanics or gas exchange.

Conclusions and Clinical Relevance

Previous studies have suggested that prerace administration of furosemide may have a positive effect on performance. Results of this study indicate that this may be attributable, in part, to an increase in mass-specific V⃙o2max but not to improvements in breathing mechanics or gas exchange. Most of the increase in mass-specific V⃙o2max appeared to be attributable to weight loss associated with diuresis induced by furosemide. (Am J Vet Res 1999;60:1415–1422)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the interobserver variability of assessment of exercise-induced pulmonary hemorrhage (EIPH) during tracheobronchoscopic examination in horses.

Animals—747 Thoroughbred racehorses.

Procedure—850 tracheobronchoscopic examinations were performed within 2 hours of racing for the horses. Examinations were recorded on videotape, and EIPH and its severity were assessed independently by 3 veterinarians. Concordance was determined by calculation of the Cohen weighted κ statistic and tabulation of scores assigned by each observer.

Results—Weighted κ statistics ranged from 0.75 to 0.80. In 99.4% of observations, all observers agreed or 2 of 3 agreed and the third differed by ≤ 1 grade.

Conclusions and Clinical Relevance—Results indicated that interobserver reliability of tracheobronchoscopic assessment of EIPH in Thoroughbred racehorses is high when the examination is conducted by experienced veterinarians. Concordance among investigators is sufficient to justify use of this grading system for further studies and clinical descriptions of EIPH. (Am J Vet Res 2005;66:596–598)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether exercise-induced pulmonary hemorrhage (EIPH) was associated with racing performance in Thoroughbred horses not medicated with furosemide and not using nasal dilator strips.

Design—Observational cross-sectional study.

Animals—744 two- to 10-year-old Thoroughbred horses racing in Melbourne, Australia.

Procedure—Horses were enrolled prior to racing, and a tracheobronchoscopic examination was performed after 1 race. Examinations were recorded on videotape, and presence and severity (grade 0 to 4) of EIPH were subsequently determined by 3 observers blinded to the horses' identity. Race records were abstracted for each horse examined.

Results—Overall, 52.1% of horses eligible for participation in the study were examined, and horses that were examined did not differ from horses that were not examined in regard to age, sex distribution, or proportion of horses that won or finished in the first 3 positions. Horses with EIPH grades ≤ 1 were 4.0 times as likely to win, 1.8 times as likely to finish in the first 3 positions, and 3.03 times as likely to be in the 90th percentile or higher for race earnings as were horses with grades ≥ 2. Horses with EIPH grades ≥ 1 finished significantly farther behind the winner than did horses without EIPH. However, odds that horses with grade 1 EIPH would win or finish in the first 3 positions were not significantly different from odds for horses without EIPH.

Conclusions and Clinical Relevance—Results suggest that EIPH is associated with impaired performance in Thoroughbred racehorses not medicated with furosemide and not using nasal dilator strips. ( J Am Vet Med Assoc 2005;227:768–774)

Full access
in Journal of the American Veterinary Medical Association